Cement compositions comprising aqueous latex containing dispersed solid and liquid elastomer phases

ABSTRACT

A composition for use as a latex cement additive, the composition comprising an aqueous latex, the aqueous latex comprising an aqueous fluid and a solid elastomer, where the solid elastomer is dispersed in the aqueous fluid; a liquid elastomer, the liquid elastomer having a viscosity between 50,000 cP and 300,000 cP at room temperature; and a surfactant, the surfactant operable to facilitate incorporation of the liquid elastomer into the aqueous latex.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Non-Provisional patentapplication Ser. No. 15/870,374 filed on Jan. 12, 2018. For purposes ofUnited States patent practice, this application incorporates thecontents of the non-provisional patent application by reference in itsentirety.

TECHNICAL FIELD

Disclosed are compositions and methods for use with cement.Specifically, disclosed are compositions and methods for enhancingcement properties in a downhole environment.

BACKGROUND

Upon completion of drilling a well, cement slurries are pumped down thehole, and placed in the annulus between a casing pipe and subterraneanformation, or between two casing strings. The cement slurry upon settingcan isolate the cemented formation zones and can prevent fluidcommunication (often referred to as zonal isolation) between thecemented zones, or between the formation and the wellbore annulus.However, the cement sheath, during the production phase of the well, issubjected to a variety of stresses from the wellbore side, such ascyclic pressure and temperature changes, fluid density changes,stimulation operations such as perforations, fracturing, acidizing andremedial operations. As a result, the cement may develop cracks andfractures which can provide conductive pathways or channels, throughwhich formation fluids can flow into, accumulate, and build pressure atthe well head. Because of the hazards posed by such situations, wellsmay need to be shut down until successful remedial operations such assqueeze cementing, or settable resin injection are carried out. Thesuccess of such remedial operations is not always assured orpredictable.

Current approaches to develop cement compositions which are, primarily,resistant to cyclic stresses and sudden impact events during the life ofthe well, and secondarily to self-heal in case of cracking under stressare complex or only mildly effective. For example, some approaches toimprove cyclic stress resistance of cement compositions include usingfoamed cement slurries, which require highly specialized equipment suchas cryogenic equipment to supply nitrogen. Other approaches such asinclusion of particulate elastomers, while representing a simplersolution, suffer from problems such as poor adhesion between cement andliquid elastomer, phase separation in the slurry, or difficulties inobtaining in suitable particle sizes.

SUMMARY

Disclosed are compositions and methods for use in cement slurries.Specifically, disclosed are compositions and methods for controlling adownhole environment during cement operations.

In a first aspect, a composition for use as a latex cement additive isprovided. The composition includes an aqueous latex, the aqueous latexincludes an aqueous fluid and a solid elastomer dispersed in the aqueousfluid. The composition further includes a liquid elastomer having aviscosity between 50,000 centiPoise (cP) and 300,000 cP at roomtemperature, and a surfactant operable to facilitate incorporation ofthe liquid elastomer into the aqueous latex.

In certain aspects, the solid elastomer includes monomers selected frombutadiene monomers, styrene monomers, acrylonitrile monomers, ethylenemonomers, vinyl acetate monomers, and combinations of the same. Incertain aspects, the liquid elastomer includes a low molecular weightpolymer, where the low molecular weight polymer includes butadiene. Incertain aspects, the low molecular weight polymer includes polar groupsselected from the group consisting of polar monomers, polar functionalgroups, and combinations of the same. In certain aspects, the lowmolecular weight polymer includes polar monomers selected from the groupconsisting of acrylonitrile, maleic anhydride, vinyl acetate, andcombinations of the same. In certain aspects, the low molecular weightpolymer includes the polar functional group selected from the groupconsisting of carboxylate groups, hydroxyl groups, carboxy anhydridegroups, ester groups, sulfonate groups, phosphonate groups, andcombinations of the same. In certain aspects, the surfactant is selectedfrom the group consisting of anionic surfactants, non-ionic surfactants,and combinations of the same. In certain aspects, where the surfactantis an anionic surfactant selected from the group consisting of sodiumdodecylbenzene sulfonate, sodium lauryl sulfonate, a sulfate salt of anonylphenol ethoxylate containing 20-40 moles of ethylene oxide. Incertain aspects, the surfactant is a non-ionic surfactant, where thenon-ionic surfactant is a nonylphenol ethoxylates containing 20-40 molesof ethylene oxide. In certain aspects, the composition further includesa latex additive.

In a second aspect, a composition for use as a cement slurry compositionin downhole cementing applications is provided. The composition includesa latex cement additive, the latex cement additive includes an aqueouslatex, the aqueous latex includes an aqueous fluid and a solid elastomerdispersed in the aqueous fluid, a liquid elastomer having a viscositybetween 50,000 cP and 300,000 cP at room temperature, and a surfactantoperable to facilitate incorporation of the liquid elastomer. Thecomposition further includes a cement composition operable to hardenedinto a set cement, the cement composition includes a cement and water.

In certain aspects, the cement is selected from the group consisting ofPortland cements, high alumina cements, magnesia cements, pozzolaniccements, and slag cements. In certain aspects, the composition furtherincludes a cement additive selected from the group consisting of acement dispersant, set retarders or accelerators, fluid loss controlagents, gas migration control additives, settling prevention additionadditives, strength retrogression prevention additives, mechanicalproperty modifiers, fibers, foaming agents, defoamer additives, andcombinations of the same.

In a third aspect, a method of making a cement slurry composition isprovided. The method includes the steps of adding an amount of a liquidelastomer to an aqueous latex to produce a latex cement additive, mixingthe latex cement additive, such that the liquid elastomer forms adispersed phase in the aqueous fluid, adding an amount of a latex cementadditive to a cement composition, and mixing the latex cement additiveinto the cement composition to form the cement slurry composition.

In certain aspects, the method further includes the steps of adding anamount of a cement to water to produce the cement composition, andmixing the cement composition.

In a fourth aspect, a method of using a cement slurry composition in adownhole application in a wellbore is provided. The method includes thesteps of adding an amount of a liquid elastomer to an aqueous latex toproduce a latex cement additive, mixing the latex cement additive, suchthat the liquid elastomer forms a dispersed phase in the aqueous fluid,adding an amount of the latex cement additive to a cement composition,mixing the latex cement additive into the cement composition to form thecement slurry composition, introducing the cement slurry composition toa wellbore, and allowing the cement slurry composition to harden into aset cement.

In certain aspects, the downhole application is selected from the groupconsisting of primary cementing operations, annulus sealing operations,and combinations of the same.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the scope willbecome better understood with regard to the following descriptions,claims, and accompanying drawings. It is to be noted, however, that thedrawings illustrate only several embodiments and are therefore not to beconsidered limiting of the scope as it can admit to other equallyeffective embodiments.

FIG. 1 provides a Thermogravimetric Analysis (TGA) graph of the aqueouslatex additive of Example 1.

In the accompanying FIGURES, similar components or features, or both,may have a similar reference label.

DETAILED DESCRIPTION

While the scope of the apparatus and method will be described withseveral embodiments, it is understood that one of ordinary skill in therelevant art will appreciate that many examples, variations andalterations to the apparatus and methods described here are within thescope and spirit of the embodiments.

Accordingly, the embodiments described are set forth without any loss ofgenerality, and without imposing limitations, on the embodiments. Thoseof skill in the art understand that the scope includes all possiblecombinations and uses of particular features described in thespecification.

The compositions and methods are directed to compositions of latexcement additives. The latex cement additives provide a method for addinga liquid elastomer to cement compositions, where the liquid elastomersalone or in pure form are not pourable and cannot be mixed with cementcompositions.

Advantageously, the latex cement additives described here enhance themechanical properties of the cement, such as by lowering the elasticmodulus, improving the tensile strength, and improving the compressivestrength. Lowering the elastic modulus of cement reduces the cementbrittleness, which is an advantage in cementing zones that produce gaswith gas flow potentials and formation gas pressures in ranges that cancause concern for production. Advantageously, the liquid elastomer inthe latex cement additive can flow into cracks and fractures in thecement, such as cracks in the cement column, microannulus at the casingto cement interface, and microannulus at the cement to cement interfacein a crack. Advantageously, the liquid elastomer in the latex cementadditive can absorb and dissipate imposed stresses better than solidelastomers. Advantageously, the elastomer content of latex cementadditives add stress-resistant properties and self-sealing properties toset cement. Stress-resistance improves the life of the set cement underthe downhole conditions due to the stresses placed on the set cement dueto the pressure conditions in the well, including the changing pressureconditions during the course of production. Self-sealing propertiesenables set cement to maintain or retain the stress-resistance and flowblocking abilities in the event of a fracture or crack in the cement; insome instances the presence of the latex cement additives can seal orclose those fractures or cracks. Advantageously, the latex cementadditives can provide fluid loss and gas migration control, whileimproving the mechanical properties of a set cement. The set cement canprovide stress-resistance and impact-resistance while providing zonalisolation. Advantageously, the latex cement additives can haveself-healing properties.

As used throughout, “latex” refers to an aqueous emulsion of a dispersedsolid polymer phase.

As used throughout, “liquid elastomer” refers to low molecular weightpolymers which are liquid at room temperature with viscosities in therange from 50,000 cP to 300,000 cP at room temperature, alternatelybetween 100,000 cP and 300,000 cP, alternately between 200,000 cP, andalternately between 100,000 cP and 200,000 cP. The liquid elastomercontains only elastomer and does not contain water or an aqueous fluid.The low molecular weight polymers can have molecular weights in therange of 1,000 to 250,000 Daltons (Da) and exist in liquid state at roomtemperature. The low molecular weight polymers can include butadienemonomer and combinations of butadiene monomer and between one and threeadditional monomers. In at least one embodiment, the low molecularweight polymer is a homopolymer including butadiene monomer alone. In atleast one embodiment, the low molecular weight polymer is a copolymerincluding butadiene and between one and three additional monomers. Theadditional monomers in the copolymer can be incorporated into thebackbone of the polymer chain or grafted onto the polymer backbone. Forexample, the butadiene monomer can polymerize by 1,4 addition duringchain growth, leading to liquid elastomers containing 2-butene groups,alternately the butadiene monomer can polymerize by 1,2-addition duringchain growth, leading to liquid elastomers containing vinyl groups.Examples of the additional monomers can include polar monomers,non-polar monomers, and combinations of the same. Examples of polarmonomers can include acrylonitrile, maleic anhydride, vinyl acetate, andcombinations of the same. Examples of non-polar monomers can includestyrene, alpha-methylstyrene, propylene, and combinations of the same.The low molecular weight polymers can be chain-end terminated with polarfunctional groups. Examples of polar functional groups can include aminogroups, carboxylate groups, hydroxyl groups, carboxy anhydride groups,ester groups, sulfonate groups, phosphonate groups, and combinations ofthe same. The polar groups from the polar monomers and polar functionalgroups are capable of binding with or adsorbing onto cement surfaces.The polar groups from the polar monomers and polar functional groups canhave a binding affinity for polyvalent metal ions and hydroxyl groupspresent in the cement and subterranean formation surfaces. Examples ofpolyvalent metal ions can include calcium, magnesium, aluminum, andcombinations of the same. Examples of the hydroxyl groups can includesilanol groups with the form R—Si—OH. Due to the polar groups, theliquid elastomers can adhere to metal surfaces, cement surfaces, andboth metal and cement surfaces.

The latex cement additive described here include an aqueous latex, aliquid elastomer and a surfactant.

The aqueous latex includes an aqueous fluid and a solid elastomer. Theaqueous latex can be any type of preformed latex containing the solidelastomer dispersed in the aqueous fluid forming an emulsion. The amountof aqueous fluid in the aqueous latex can be about 50 percent (%) byweight. The aqueous latex can be formed by polymerization of monomers inan emulsion polymerization process, where the polymerization of monomersforms the dispersed solid elastomer. The aqueous fluid is pure water.

The solid elastomer can be any film forming elastomer containingbutadiene monomers, styrene monomers, acrylonitrile monomers, ethylenemonomers, vinyl acetate monomers, and combinations of the same. In atleast one embodiment, the solid elastomer includes butadiene monomer,styrene monomer, acrylonitrile monomer, and combinations of the same. Inat least one embodiment, the solid elastomer includes a combination ofethylene monomer and vinyl acetate monomer. The ratio of the differentmonomers can vary depending on the solid elastomer. The solid elastomercan also include a polar monomer in an amount between 1% by weight and10% by weight. Examples of polar monomers include acrylic acid salt and2-acrylamide-2-methyl propane sulfonic acid salt. The polar monomer canbe present to reinforce the stability of the emulsion of the aqueouslatex. Advantageously, film forming elastomers can have gas migrationcontrol and fluid loss control.

The aqueous latex can be a commercially available aqueous latex.Examples of commercially available aqueous latexes can includestyrene-butadiene latexes, acrylonitrile butadiene latexes, andpolyvinyl acetate latexes. Commercially available styrene-butadienelatexes typically have proprietary monomer ratios.

In some embodiment, the aqueous latex can include a latex additive.Examples of latex additives can include stabilizing surfactants,rheology modifiers, viscosifiers, and combinations of the same. Thelatex additive can be present in the aqueous latex in an amount of about10% by weight.

The surfactant can be any type of surfactant capable of facilitating theincorporation of the liquid elastomer in the aqueous latex andstabilizing the latex cement additive. Examples of the surfactant caninclude anionic surfactants, non-ionic surfactants and combinations ofthe same. Examples of anionic surfactants can include sodiumdodecylbenzene sulfonate, sodium lauryl sulfonate, a sulfate salt of anonylphenol ethoxylate containing 20-40 moles of ethylene oxide, andcombinations of the same. Examples of the non-ionic surfactants caninclude a nonylphenol ethoxylate containing 20-40 moles of ethyleneoxide.

The latex cement additive can be formed by adding the liquid elastomerand surfactant to the aqueous latex. The liquid elastomer and surfactantcan be mixed in one step or added separately. In at least oneembodiment, the surfactant is added first, followed by the liquidelastomer with vigorous stirring. Adding the surfactant first can resultin a better dispersion of the mixture. In at least one embodiment, themixture can be heated to a temperature of greater than 140 deg F. andalternately a temperature between 140 deg F. and 180 deg F. Heating themixture can accelerate the dispersion of the liquid elastomer in theaqueous latex. The components can be mixed until the liquid elastomer isincorporated into the aqueous latex forming a stable emulsion. A stableemulsion is achieved when the mixture does not phase separate into anaqueous phase and non-aqueous phase for at least 24 hours. Thecomponents can be mixed for a time between 2 hours and 24 hours. In atleast one embodiment, the latex cement additive can be an emulsion,where the liquid elastomer is incorporated into the dispersed phase withthe solid elastomer. In at least one embodiment, the latex cementadditive can be an emulsion, where the liquid elastomer is incorporatedinto the aqueous latex as an internal phase separate from the dispersedsolid elastomer. In at least one embodiment, the dispersed phase canreach a total volume fraction of between 70 percent and 75 percent ofthe latex cement additive.

Cement slurry compositions can include the latex cement additives and acement composition. The cement composition can include a cement andwater. The cement can be any cement capable of being used in downholeapplications. Examples of cements can include Portland cements, highalumina cements, magnesia cements, pozzolanic cements, and slag cements.In at least one embodiment, the cement is a Portland cement, and thePortland cement is a Class G cement. The cement slurry composition caninclude cement additives. Examples of cement additives include a cementdispersant, set retarders or accelerators, fluid loss control agents,gas migration control additives, settling prevention addition additives,strength retrogression prevention additives, mechanical propertymodifiers, fibers, foaming agents, defoamer additives, and combinationsof the same.

In at least one embodiment, the latex cement additives can be mixed withthe water prior to the cement being mixed with the water to produce thecement slurry composition. In at least one embodiment, the latex cementadditives can be mixed with the cement composition. Cement additivesthat are solid additives can be dry blended with the cement prior to thecement being added to the water and alternately water containing thelatex cement additives.

The amount of each component of the cement slurry composition can bedetermined based on the down hole conditions, including the temperature,formation pressure and fracture gradient of the formation. Additionally,the amount of each component of the cement slurry composition can bedetermined based on whether the slurry is the lead of the slurry columnor the tail of the slurry column.

The cement slurry compositions can be used in downhole applications.Examples of downhole applications include primary cementing operationsand annulus sealing operations. Annulus sealing operations can includesealing an annulus between a casing and a formation, alternately betweentwo casings, and alternately between a casing and a liner.

EXAMPLES Example 1

In Example 1, Samples 1-3 were formulations of the latex cement additiveand Sample 4 was a comparative example. The aqueous latexes tested werecommercially available: Verilok 552 (formerly Genceal CM 8400) availablefrom OMNOVA SOLUTIONS (Beachwood, Ohio), a sulfonated styrene butadienelatex; Latex 2000 available from Halliburton (Houston, Tex.) acarboxylated styrene butadiene elastomer latex; and TYLAC® 4901available from Mallard Creek Polymers (Charlotte, N.C.) a carboxylatedstyrene butadiene elastomer latex. Each of the aqueous latexes containedabout 40% by weight dispersed solid elastomer, about 10% non-elastomerproprietary components, such as surfactants, and about 50% water. Theemulsifier was Latex Stabilizer-RS from RITEKS Corporation (McKinney,Tex.), an anionic emulsifier. The liquid elastomer was a polybutadienechain-end terminated with carboxylate groups having a molecular weightof 4300 Da.

The samples were created by adding the emulsifier, according to Table 1,and stirring. The liquid elastomer was added with a spatula in an amountaccording to Table 1. The resulting mixture was stirred for 2 hoursuntil the liquid elastomer was dispersed or emulsified uniformly.

TABLE 1 Formulations of Samples 1-3 Sample Aqueous Latex EmulsifierLiquid Elastomer Sample 1 Verilok 552 - 5 milliliters (mL) 11.0 g 102.4grams (g) (5% by weight) (10-12% by weight) Sample 2 Latex 2000 - 5 mL11.0 g 102. 4 g (5% by weight) (10-12% by weight) Sample 3 Tylac 4901 -5 mL 11.0 g 102.4 g (5% by weight) (10-12% by weight)

After stirring for 2 hours, no non-emulsified liquid elastomer wasobserved in Sample 1. Similar results were observed in Samples 2 and 3,no non-emulsified liquid elastomer was observed after stirring. Thermalgravimetric analysis was used to analyze the solid content of Sample 1.As can be seen in FIG. 1, the thermal gravimetric analysis showed atotal polymer concentration in the latex cement additive of about 58% byweight of the latex cement additive. In contrast, the Verilok 552sample, without the liquid elastomer, contained about 40% elastomer. Theresults indicate the latex cement additive contained about 18% liquidelastomer emulsified in the aqueous latex. The samples were allowed tosit statically for 6 months and no phase separation was observed,indicating the latex cement additive was stable.

Sample 4 was a comparative example that included water in place of theaqueous latex. The same emulsifier and liquid elastomer as used inSamples 1-3 were used in Sample 4. Five mL of Latex Stabilizer-RSemulsifier was mixed with 95 mL of water and stirred. Eleven g of theliquid elastomer was added to the mixture and stirring continued. Evenafter a prolonged period of 76 hours of vigorous stirring, the mixturewas milky and had large lumps of the liquid elastomer, with the liquidelastomer forming an emulsified elastomer phase. Upon storage understatic conditions, the emulsified elastomer phase separated from thewater and formed a sticky layer on top of the emulsion. In an additionalstep, the commercially available aqueous latex, Verilok 552 was added inincreasing amounts up to 25 mL aliquots to the phase separated emulsionand stirred, but the phase separated mixture did not emulsify the liquidelastomer. When compared to Samples 1-3, it appears that the liquidelastomer must be added to the aqueous latex for effectiveemulsification.

Example 2

Example 2 was a study of the latex cement additive in cementcompositions. The cement in Example 2 was a class G Portland cement fromSaudi Arabia. The aqueous latex was Latex 2000 available fromHalliburton (Houston, Tex.). The surfactant was Stabilizer 434B LatexStabilizer available from Halliburton (Houston, Tex.). The defoameradditive was D-Air 3000 available from Halliburton (Houston, Tex.). Thecement dispersant was CFR-3 available from Halliburton Energy Services(Houston, Tex.).

Sample 5 of Example 2 was a comparative sample containing a 16.0 poundsper gallon (ppg) cement composition containing the cement and water.Sample 1 was prepared according to API Recommended Practice 10B-2.

Sample 6 was a comparative sample containing a 16.0 ppg cementformulation containing the cement (1600 g), water (670 mL), the cementdispersant, the aqueous latex (Latex 2000-140 g), the surfactant (10mL), and the defoamer additive (3 mL). The content of solid elastomer inthe cement formulation was 4% by weight of cement. Sample 6 was preparedby addition of the defoamer, aqueous latex, and the surfactant to mixwater in a Waring blender while stirring at 1000 revolutions per minute(rpm). In a next step, the cement and the cement dispersant were mixedinto the fluid. The cement formulation was then cured at 180 degreesFahrenheit (deg F.) in an autoclave under a pressure of 3000 pounds persquare inch (psi) for 76 hours.

Sample 7 was a 16.0 ppg cement slurry containing the cement (1600 g),water (670 mL), the cement dispersant, the latex cement additive, thesurfactant (10 mL), and the defoamer additive (3 mL). The latex cementadditive of Sample 7 was prepared by mixing the liquid elastomer, thepolybutadiene chain-end terminated with carboxylate groups from Example1, with the aqueous latex, Latex 2000, to produce a latex cementadditive having a concentration of 60% by weight of the latex cementadditive as described in Example 1. Sample 7 was prepared by addition ofthe defoamer, latex cement additive, and the surfactant to mix water ina Waring blender while stirring at 1000 revolutions per minute (rpm). Ina next step, the cement and the cement dispersant were mixed into thefluid to produce the cement slurry. The amount of total elastomer in thecement slurry was 4% by weight of cement (% bwoc). The cement slurry waspoured into 1.5 inch by 9 inch steel molds and then cured at 180 degreesFahrenheit (deg F.) in an autoclave under a pressure of 3000 pounds persquare inch (psi) for 76 hours. The steel molds produced cylindricalsamples, which were cut into 1.5 inch by 3 inch cylinders for use in thecompressive strength measurements and 1.5 inch by 1 inch cylinders foruse in the tensile strength measurements.

The tensile strength of each sample was measured by the Brazilian SplitCylinder test and the compressive strength was measured on Forneyequipment under a load rate of 336 pounds force per second. The resultsof the tests are shown in Table 2.

TABLE 2 Results of tests in Example 2. Liquid Elastomer/ Total AverageAverage Solid Elastomer Tensile Compressive CS to Elastomer ContentStrength, TS Strength, CS TS (% bwoc) (% bwoc) (psi) (psi) ratio Sample5 0 0 660 6610 10.0 Sample 6 0/4 4 490 4880 10.0 Sample 7 1.75/2.25 4620 4230 6.80

The results show that Sample 6 and Sample 7 show decreased compressivestrengths due to the reduced brittleness as compared to Sample 5. Thefurther decrease in compressive strength in Sample 7 as compared toSample 6 indicates a possible lower Young's modulus (YM). Sample 7 showsa tensile strength higher than that for Sample 6. The compressivestrength to tensile strength ratio (CS/TS) indicates the beneficialaspects of adding the latex cement additive to cement compositions,where the latex cement additive includes the liquid elastomerscontaining functional groups capable of bonding with cement. The resultsof Sample 5 are typical of conventional cement compositions typicallyhaving compressive to tensile strength ratios of about 10 or greater.The decreased C/S ratio of Sample 7 would increase the ability of thecement slurry composition of Sample 7 to decrease the susceptibility ofthe cement slurry composition to tensile failure of the cement sheathunder imposed tensile stresses in a wellbore. Imposed tensile stressescan stem from expansion of the casing due to fluid pressure in thewellbore or increase in temperature during the production phase. Sample7 illustrates the stress-resistant properties of the latex cementadditives.

Example 3

In Example 3, four latex cement additives were prepared (Samples 9, 10,11, and 12), along with a control sample (Sample 8) using the sameprocedures and components of Example 1. The liquid elastomer in Sample 9was a polybutadiene chain-end terminated with carboxy groups having amolecular weight of 4300 purchased from Sigma Aldrich Chemical Company(St. Louis, Mo.). The liquid elastomer in Sample 10 was a copolymer ofacrylonitrile and butadiene containing 18% by weight acrylonitrile andchain-end terminated with carboxy groups having a molecular weight of3600 purchased from Sigma Aldrich Chemical Company (St. Louis, Mo.). Theliquid elastomer in Sample 11 was a polybutadiene chain-end terminatedwith hydroxy groups having a molecular weight of 2400 purchased fromSigma Aldrich Chemical Company (St. Louis, Mo.). The liquid elastomer inSample 12 was a polybutadiene grafted with maleic anhydride containing13% by weight maleic anhydride and having a molecular weight of 3100,available under the product name Ricon 130MA13 from Cray Valley (Exton,Pa.). Sample 8, the control sample, contained the aqueous latex, but noliquid elastomer. The aqueous latex was a styrene-butadiene latex,available under the name Tylac 4901 from Mallard Creek Polymers(Charlotte, N.C.). For each of samples 9-12, the latex cement additiveswere prepared by mixing the aqueous latex and the liquid elastomer andheating to a temperature between 140 deg F. and 180 deg F. for 1 to 2hours followed by stirring the heated mixture for 18 hours to obtain ahomogenous stable emulsion. Cement compositions using the latex cementadditives were prepared as described in Example 2.

Each cement slurry composition was prepared with 1600 g Class G Portlandcement, 670 g water, 140 g of the latex cement additive, 3 mL of adefoamer, 2-ethyl hexanol. Samples 10 and 12 included 10 mL of astabilizing surfactant, stabilizer 434B from Halliburton (Houston,Tex.). Samples 9 and 11 included an additional 10 g of water, but didnot include the stabilizing surfactant. Sample 8 contained 160 g of theaqueous latex and 654 g of water. The density of each cement slurrycomposition was 15.4 pounds per gallon (ppg). Each cement slurrycomposition contained 4% total elastomer. The cement slurry compositionswere poured into 2 inch by 5 inch steel molds and allowed to cure for 72hours at 180 deg F. under a pressure of 3000 psi to produce cylinders.The cylinders were cut into 2 inch by 4 inch cylinders for thecompressive strength tests and Young's modulus measurements and 2 inchby 1 inch cylinder discs were prepared for the tensile strength measureswith the Brazilian Split Cylinder method. The self-sealing ability wasdetermined by wrapping the split halves of the samples from the tensilestrength measurements in a piece of aluminum foil, holding the piecetogether in a C-Clamp and heating the sample at 200 F for 48 hours. Theheated samples were cooled and hand pressure was applied on theself-healed sample in an attempt to break the sample. The relative easewith which the sample is split is ranked for all the formulations. Theresults are shown in Table 2.

TABLE 2 Properties of Samples of Example 3 Sample Sample Sample SampleSample 8 9 10 11 12 Liquid Elastomer, 0 1.75 1.75 1.75 1.75 % bwoc SolidElastomer 4 2.25 2.25 2.25 2.25 from Latex, % by weight Total Elastomer,4 4 4 4 4 % by weight Stabilizing Surfactant, 1.53 1.53 0 0 0 % byweight of mix water Compressive Strength 4650 3840 4350 4170 4470 (CS),psi Tensile Strength (TS), 410 380 470 410 370 psi CS/TS Ratio 11.0 10.09.0 10.0 12.0 Young's Modulus (YM), 1.90 × 1.48 × 1.77 × 1.75 × 1.29 ×psi 10⁶ 10⁶ 10⁶ 10⁶ 10⁶ Self-healing ability Poor Poor Poor Poor Good

Although the embodiments have been described in detail, it should beunderstood that various changes, substitutions, and alterations can bemade hereupon without departing from the principle and scope.Accordingly, the scope of the embodiments should be determined by thefollowing claims and their appropriate legal equivalents.

There various elements described can be used in combination with allother elements described here unless otherwise indicated.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed here as from about one particular value to aboutanother particular value and are inclusive unless otherwise indicated.When such a range is expressed, it is to be understood that anotherembodiment is from the one particular value to the other particularvalue, along with all combinations within said range.

As used here and in the appended claims, the words “comprise,” “has,”and “include” and all grammatical variations thereof are each intendedto have an open, non-limiting meaning that does not exclude additionalelements or steps.

That which is claimed is:
 1. A method of using a cement slurry composition in a downhole application in a wellbore, the method comprising the steps of: adding an amount of a liquid elastomer to an aqueous latex to produce a latex cement additive; mixing the latex cement additive, such that the liquid elastomer forms a dispersed phase in the aqueous fluid; adding an amount of the latex cement additive to a cement composition; mixing the latex cement additive into the cement composition to form the cement slurry composition; introducing the cement slurry composition to the wellbore in the downhole application; and allowing the cement slurry composition to harden into a set cement.
 2. The method of claim 1, where the downhole application is selected from the group consisting of primary cementing operations, annulus sealing operations, and combinations of the same.
 3. The method of claim 1, where the aqueous latex comprises an aqueous fluid and a solid elastomer, where the solid elastomer is dispersed in the aqueous fluid.
 4. The method of claim 3, where the solid elastomer comprises monomers selected from butadiene monomers, styrene monomers, acrylonitrile monomers, ethylene monomers, vinyl acetate monomers, and combinations of the same.
 5. The method of claim 1, where the liquid elastomer has a viscosity between 50,000 cP and 300,000 cP at room temperature.
 6. The method of claim 5, where the liquid elastomer comprises a low molecular weight polymer having a molecular weight in the range of 1,000 Daltons (Da) to 250,000 Da, where the low molecular weight polymer comprises butadiene.
 7. The method of claim 6, where the low molecular weight polymer having a molecular weight in the range of 1,000 Da to 250,000 Da comprises polar groups selected from the group consisting of polar monomers, polar functional groups, and combinations of the same.
 8. The method of claim 6, where the low molecular weight polymer having a molecular weight in the range of 1,000 Da to 250,000 Da comprises polar monomers selected from the group consisting of acrylonitrile, maleic anhydride, vinyl acetate, and combinations of the same.
 9. The method of claim 6, where the low molecular weight polymer having a molecular weight in the range of 1,000 Da to 250,000 Da comprises the polar functional group selected from the group consisting of carboxylate groups, hydroxyl groups, carboxy anhydride groups, ester groups, sulfonate groups, phosphonate groups, and combinations of the same.
 10. The method of claim 1, where the cement composition comprises a cement and water.
 11. The method of claim 10, where the cement is selected from the group consisting of Portland cements, high alumina cements, magnesia cements, pozzolanic cements, and slag cements.
 12. The method of claim 1, where the latex cement additive further comprises a surfactant.
 13. The method of claim 12, where the surfactant is selected from the group consisting of anionic surfactants, non-ionic surfactants, and combinations of the same.
 14. The method of claim 12, where the surfactant is an anionic surfactant selected from the group consisting of sodium dodecylbenzene sulfonate, sodium lauryl sulfonate, a sulfate salt of a nonylphenol ethoxylate containing 20-40 moles of ethylene oxide.
 15. The method of claim 12, where the surfactant is a non-ionic surfactant, where the non-ionic surfactant is a nonylphenol ethoxylates containing 20-40 moles of ethylene oxide. 